Internal combustion engine

Abstract

In an internal combustion engine which is alternatively operated in a powered four-stroke engine driving mode and in a two-stroke engine braking mode with an inlet and an outlet valve stroke curve control device which is provided for adjusting the stroke of both the inlet and of the outlet valves, the valve stroke curve control device holds the outlet valve continuously open in the engine braking mode.

1 . An internal combustion engine with cylinders having inlet and outlet valves ( 3 ,  7 ) for controlled communication with inlet and outlet passages for operating the engine alternatively in a spark-ignited four-stroke driving mode and in a two-stroke engine braking mode, wherein combustion air is fed to the cylinders ( 1 ), to be compressed in the cylinders ( 1 ) and subsequently expelled into an exhaust duct ( 16 ), whereby, in the expansion phase of the cylinders ( 1 ) the inlet valves ( 5 ) are opened before the bottom dead center (UT) is reached and are closed again after the bottom dead center (UT) has been passed, and the outlet valves ( 7 ), which open into the exhaust duct ( 16 ) are moved to an open position, said engine including a stroke curve adjustment device ( 22 ) for adjusting stroke curves (EV, AV) of both the inlet valves ( 5 ) and of the outlet valves ( 7 ), with the stroke curve adjustment device ( 22 ) acting on the outlet valves ( 7 ) at the transition from the spark-ignition driving mode to the engine braking mode in such a way that the outlet valves ( 7 ) are continuously open during the entire engine braking mode, both in the expansion phase and in the compression phase. 
   
   
       2 . The internal combustion engine as claimed in  claim 1 , wherein during changeover between the four-stroke driving mode and the two-stroke engine braking mode, the valve-stroke curve control device ( 22 ) permits a continuous transition in the stroke curves (EV, AV) of the inlet valves ( 5 ) and of the outlet valves ( 7 ). 
   
   
       3 . The internal combustion engine as claimed in  claim 1 , wherein the stroke curve control device ( 22 ) is connected to an adjustable cam shaft ( 23 ) with cams ( 24 ,  25 ) for the inlet valve ( 5 ) and the outlet valve ( 7 ) with different cam curves for the four-stroke driving mode and for the two-stroke engine braking mode arranged on the cam shaft ( 23 ). 
   
   
       4 . The internal combustion engine as claimed in  claim 3 , wherein the cam shaft ( 23 ) is axially movable for the control of the valves by the two different types of cams. 
   
   
       5 . The internal combustion engine as claimed in  claim 1 , wherein, with a common actuating movement of the stroke curve control device operated camshaft ( 23 ) the stroke curves (EV, AV) of both the inlet valves ( 5 ) and of the outlet valves ( 7 ) are adjustable between the four-stroke driving mode and the two-stroke engine braking mode. 
   
   
       6 . The internal combustion engine as claimed in  claim 1 , wherein, in the engine braking mode, the outlet valves ( 7 ) are held in a constant open position by the stroke curve control device ( 22 ). 
   
   
       7 . The internal combustion engine as claimed in  claim 1 , wherein the the camshaft ( 23 ) comprises a cylinder structure as a cam for the engine braking mode for keeping the valve in the constant open position. 
   
   
       8 . The internal combustion engine as claimed in  claim 1 , wherein the camshaft ( 23 ) for the engine braking mode includes a cone without a cam structure which is axially displaceable for adjustment of the valve stroke. 
   
   
       9 . The internal combustion engine as claimed in  claim 1 , wherein an exhaust gas turbocharger ( 2 ) is provided with a compressor ( 11 ) in the intake section ( 20 ) and an exhaust gas turbine ( 10 ) in the exhaust duct ( 16 ). 
   
   
       10 . The internal combustion engine as claimed in  claim 9 , wherein the exhaust gas turbine ( 10 ) is provided with a variable turbine geometry ( 13 ) for variably setting the effective turbine inlet cross-section, wherein, in the engine braking mode, the variable turbine geometry ( 13 ) is adjustable into a blocking position which reduces the turbine inlet flow cross-section. 
   
   
       11 . The internal combustion engine as claimed in  claim 9 , wherein a bypass ( 26 ) is provided which bypasses the exhaust gas turbine ( 10 ) and an adjustable bypass valve ( 27 ) is arranged in the bypass ( 26 ), so that the requested engine braking power in the engine braking mode can be adjusted by setting the bypass valve ( 27 ). 
   
   
       12 . The internal combustion engine as claimed in  claim 9 , wherein the variable turbine geometry ( 13 ) is embodied as a braking vane structure which is movable into the turbine inlet duct. 
   
   
       13 . The internal combustion engine as claimed in  claim 9 , wherein the exhaust gas turbocharger ( 2 ) is dimensioned in such a way, that a turbine braking factor (TBF) relating to the engine braking mode at maximum braking power of the exhaust gas turbocharger, which is determined according to the relationship
     TBF=A   T   *D   T   /V   H     
     has a value of less than 0.005 (5  0 /00): TBF<0.005, wherein
 A T =free flow cross-section in the exhaust gas path to the exhaust gas turbine ( 10 ) at maximum braking power 
 D T =turbine inlet diameter in the exhaust gas turbine 
 V H =displacement volume of the internal combustion engine.